In 1995 I was in Japan for a short while. When there I saw TV sets that had CRTs that were approx 5 by 3 aspect ratio. But at the time Japan was using their variation of NTSC, with 4 by 3 aspect ratio. So how did these TVs deal with that, you ask. The TVs essentially stretched the end 1/4 areas to fill in the 5 by 3 aspect ratio. So the center of the picture looked normal, and closer to the left and right ends the stretching was gradually ramped up to stretch the picture to fill the 5 by 3 CRT. Oh, on some images it would look okay, but forget about watching NFL football games. The lines on the field would look completely wacky. Or baseball diamonds would also look weird. It just seemed to be an ill conceived idea. But these sets seemed fairly common there, so maybe people just wanted a more modern looking TV set? Maybe they had HD line inputs, but I don't know. They wern't that big, maybe 20 inches across.

I thought it was for the Hi-Muse transmission and LaserDiscs, effectively HD.

I have a Panasonic Tau 16:9 34" HD CRT set (it can do 480i, 480p, and 1080i via component, but no 720p like many early HD sets, and no tuner at all) and it has a similar option for 4:3 sources where it keeps the center of the picture correct and only stretches the sides to fill out the screen. I don't ever use that mode except as a novelty because it looks weird if the camera pans.

And by the way, 1080i on a CRT looks spectacular. Too bad it weighs probably 400+ pounds.